Sunday, December 05, 2010

Cut Light for Long Daylight Exposures


Garrapata Dawn light, originally uploaded by Jeff Sullivan.

We've all seen those nice one or two second exposures which make waterfalls look silky. Select your smallesta aperture, set your ISO sensitivity low, and perhaps add a circular polarizer to your lens to reduce light, and those exposures should be within range. But have you considered longer daylight exposures and similarly abstracting other moving subjects such as waves?

On a recent trip to California's Big Sur coast I was shooting long pre-dawn exposures and I decided to continue with long exposures for as long as I could. I started with my wide and midrange lenses closed to their smallest aperture f/22, I gradually reduced ISO sensitivity to Low (ISO 50) as the light increased, and I added a polarizing filter to cut light. As the sky lightened I added a 3 stop graduated neutral density filter to reduce light coming from the sky.

As the day continued to brighten I continued shooting but added a 3 stop neutral density filter and eventually I changed to a 70-200mm lens to further reduce aperture another stop to f/32. I had started with a Hoya Pro1 circular polarizer which only reduces light 1 1/4 stop, so I also used a darker polarizer which cut 2 stops of light. With the polarizer plus the ND and GND filters stacked I was cutting 8 stops of light in the sky and 5 elsewhere, on a camera shooting at f/32, ISO 50.

To continue in bright, direct sunlight you'll need to settle for shorter exposure times or go further to cut the light such as with a 10 stop ND filter. But a 10 stop filter is a pretty specialized tool that might not be on the top of your wish list, so in the meantime try shooting near dusk and dawn with your smallest aperture (most likely on your longest zoom lens), stacking the light-cutting filters you already have on hand.

A few things I should mention though... if you try long shots like this, it's critical to use a sturdy tripod, a remote shutter release or your camera's self timer, and don't forget to turn your camera's image stabilization off.

As always, click on any image to see a larger copy.